Indirect field-oriented control (IFOC) is widely used for induction machines, including induction motors of vehicles. For example, IFOC is utilized in some vehicles for three-phase induction motor control of traction applications. IFOC can be a valuable tool. For example, if certain parameters are known, IFOC reduces the complex dynamics of the induction motor to the dynamics of a separately excited direct current motor. This approach allows the flux and torque of the induction motor to be controlled independently.
However, if the parameters used in IFOC are not identical to the actual parameters in the induction machine, the desired machine flux level may not be properly maintained. In addition, because the desired torque is estimated based on the actual parameters, torque linearity may also be lost. For example, it may be difficult to properly maintain decoupling between the flux and torque if less than ideal rotor resistance values are used in the calculation. Thus, rotor resistance values, which are functions of rotor temperature, can have a significant impact on the performance of IFOC. Torque accuracy, response and efficiency can similarly be affected by the accuracy of the values of rotor resistance that are used in the calculations.
Accordingly, it is desirable to provide improved methods and systems for controlling an induction motor that provide improved estimates of rotor resistance. Furthermore, other desirable features and characteristics of the present invention will be apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.